Day Light *******

I booked a vehicle online through bookings.com which was smooth and easy, I booked for 22nd Jan but due to a change I call and informed them I would pick up the following morning. 23rd Jan. Which we did. On collection at Cape Town Airport and paying a further 3161.85 which would be place on hold on my credit card, supposedly refunded on return, Avis employee told me someone would be waiting at the vehicle to do an onsite inspection with me. We waited by the vehicle for over 20 min no one came, I asked a person who worked there, passing by,what we should do they said that all would be OK, we could go- the vehicle was fine. Me and the 3 other people with me all walked around the car and it was all 100% fine. Absolutely no damage of any sort. On the day of return at 4am in the morning, I was asked to sign for dropping off the vehicle. Upon walking away i was told there was a scratch on the front bumper passenger side and i would be not getting my deposit on hold back and am liable for damages!!! I walked back and looked and asked where exactly was it as I couldn't see anything, I was told rudely to look closer and the man point to the car, I got down on my hands and knees and saw a 2cm max size scratch on the bumper as it bends towards the under carriage of the vehicle - Clearly not caused by reckless driving, accident or malicious damage, lookes like a stone from off the road or stick maybe, but not accident damage of any sort. Do Avis expect me to sweep all roads before we drive on them to make sure a stone or stick, plastic, metal off the road doesn't mark the vehicles. I addressed this concern with them but have been ignored and had and sms to say they billing me R1784.78 for damages, no call no acknowledgement of my email. Does this amount come off the deposit I paid or is it additional to the R3000 + deposit. And just to put all into perspective I traveled only about 30kms in the 5 days. Basically to my mothers care home and back daily to my accommodation, and the odd drive to get her food and meds etc.... If anyone uses Avis check your car even the underneath and take close up pics from all angles, don't sign any forms on return delivery as this is how they catch you into paying for "damages" shocking service and daylight *******!!! I want my money back!!!